This is the way I do it to find the average.
10 girls times 70 = 700
15 boys times 80= 1200
700+1200=1900 all their scores
1900÷25 (number of boys and girls)=76 or 76%
The first one is:-89
Second one is:False
I believe it's b. Hope this helps
3.15 addd all of them! Then divide
Answer: exact form: 251/56, decimal form 4.482, mixed number form 4 27/56